1. Field of the Invention
This invention relates to light emitting devices comprising a base material or protective member having flexibility, light transmittance, weather resistance, heat resistance and electrical insulation as well as improved passivation, and more particularly, to organic EL devices using the same.
2. Description of the Background
Organic EL devices have a basic configuration including a hole injecting electrode of tin-doped indium oxide (ITO) etc., a hole transporting material such as triphenyldiamine deposited thereon, a light emitting layer of a fluorescent material such as aluminum quinolinol complex (Alq3) stacked thereon, and an electrode (electron injecting electrode) of a metal having a low work function such as Mg. The devices produce a very high luminance of several 100 to several 10,000 cd/m2 when driven at a voltage of about 10 volts.
For the application of such organic EL devices to portable equipment, flexible materials such as resin film are of interest as the device base material. When highly heat resistant films such as polyimide and aramid films are used as the flexible base material, there may arise a problem that since these films are hydrophilic, outgassing due to water or moisture absorption of the films causes degradation of electrode materials and thin films such as EL film. Additionally, thin film laminates including the base material can be curled, bowed or waved. Detrimental effects are exerted on dimensional factors such as a thermal shrinkage factor and a coefficient of linear expansion and deformation.
Meanwhile, in order that organic EL devices find use as a display, their application to a color display of producing three primary colors of blue, green and red using a fluorescence conversion layer of fluorescent material and/or color filter layers is under study.
A method of constructing a color display by combining a single light emitting layer with a fluorescence conversion layer of fluorescent material and/or color filter layers is not only simple and inexpensive because only a single organic EL device is needed, but also advantageous in that a full-color display can be arrived at by forming the fluorescence conversion layer and/or the color filter layers in a desired pattern.
However, to form the fluorescence conversion layer and/or the color filter layers on the organic EL structure in a desired pattern is very difficult from the standpoints of patterning technique and damages to the organic EL structure. In an alternative wherein the fluorescence conversion layer and/or the color filter layers are formed on a substrate in a desired pattern and the organic EL structure is laid thereon, steps resulting from the patterning cause breaks or discontinuities of the overlying film or disconnection of wiring strips, which inhibits current flow with a failure to operate as an organic EL device. Another problem is that moisture and gases emanating from the fluorescence conversion layer and/or the color filter layers can damage organic layers and electrodes and corrode the electrodes.
One approach for solving these problems is to form an overcoat layer on the fluorescence conversion layer and/or the color filter layer. This approach yet leaves unsolved the problem that moisture and gases can damage organic layers and electrodes and corrode the electrodes.
Many attempts have been made to form a passivation film. These attempts are impractical for some reason or other that the moisture or gas impermeable effect of the film is insufficient, the surface flatness thereof is problematic, and the fluorescence conversion layer and/or the color filter layer or the overcoat layer serving as the underlying layer can be damaged by the conditions during formation of the passivation film.
When a passivation film is deposited by a vacuum process, the above problems may be overcome by increasing the thickness of the passivation film. However, a thick passivation film takes a long time to deposit and is poorly productive. An additional problem is that the film produced by the dry process has considerable internal stresses so that it may be readily cracked, failing to exert the passivation effect.
An object of the invention is to provide a light emitting device comprising a base material or protective member which has improved light transmittance, heat resistance, passivation (gas barrier, oligomer release prevention and minimized outgassing), anti-water or moisture-absorption, stability against chemical degradation, dimensional and shape stability, anti-surface-reflection, electrical insulation, UV degradation resistance, and weather resistance, and is highly productive due to possible film formation under atmospheric pressure, and hence, a light emitting device featuring high reliability, ease of manufacture and low cost.
This and other objects are achieved by the invention which is defined below.
(1) A light emitting device comprising a base material having at least light transparency and heat resistance, a lower electrode having light transmittance, a light emitting layer, and an upper electrode formed on the base material,
said device further comprising a silica film and/or a siliceous film which is formed on the substrate side as viewed from the light emitting layer or on opposite sides of the substrate by applying polysilazane and subjecting it to oxidative treatment.
(2) The light emitting device of above (1) wherein said base material is formed of a glass or resin material.
(3) The light emitting device of above (1) wherein the silica film and/or the siliceous film is disposed at least between said base material and said light emitting layer.
(4) The light emitting device of above (3) wherein TFT""s are formed on said base material and the light emitting layer is disposed on the TFT""s.
(5) The light emitting device of any one of above (1) to (4) wherein the silica film and/or the siliceous film is disposed at least on opposite sides of the substrate.
(6) The light emitting device of any one of above (1) to (5) wherein the silica film and/or the siliceous film has been subjected to oxidative treatment under heated and/or humidified conditions.
(7) The light emitting device of any one of above (1) to (6) wherein said polysilazane and/or a modified product thereof has a structural unit of the following structural formula: 
wherein R1, R2 and R3 are alkyl groups, and at least one of R1, R2 and R3 is a hydrogen atom.
(8) The light emitting device of above (7) wherein the total number of carbon atoms in the alkyl groups is up to 6.
(9) The light emitting device of (7) or (8) wherein said silica film and/or said siliceous film is obtained by converting a polysilazane having a number average molecular weight of 100 to 50,000 and/or a modified product thereof into a ceramic.
(10) The light emitting device of any one of above (1) to (9) which is an EL device.
In embodiment (1), a more stable Si3N4 film can be obtained by heat treatment in vacuum.
In embodiments (2) and (3), by forming a SiOxNy film between a color filter and the transparent lower electrode, the device can be protected from outgassing from the color filter or the like.
In embodiments (4) and (5), gases emanating from the substrate can be blocked by the passivation film.
In embodiment (6), even a thick passivation film can be easily formed without using a vacuum chamber for sputtering or the like.
In embodiments (7), (8) and (9), the film becomes so flexible that no cracks occur in a film of 1.0 micron thick although cracks occur in a conventional film of even 0.5 micron thick. Among the alkyl groups, simple alkyl groups such as methyl are preferred.